This invention relates to an apparatus for catching flying insects, particularly insects harmful in forests, such as bark beetles. The apparatus has a hollow body which, in use, has a substantially vertically oriented wall structure provided with a plurality of independent, spaced openings and a receptacle (dispenser) disposed in the hollow body and containing a volatile compound serving as an attractant.
Damage to forests caused by insects, particularly bark beetles is significant. Certain species of bark beetles kill evergreen trees, while others diminish the quality of cut wood stored in the forest. In the fight against bark beetles large volumes of cut evergreen wood are treated with poison to prevent breeding of the beetles in the logs or to destroy the offspring. Such poison, however, often destroys useful or harmless insects or other small animals whereby the ecological balance of the forest is adversely affected. In addition, laws concerning the protection of drinking water often significantly limit the use of poisons. Since the economic significance of bark beetles is expected to expand further inasmuch as industrial emissions (such as acid rain) make the trees more prone to insect attacks, a certain urgency is developing to find effective non-poisonous means to control the bark beetles.
More recently for certain insect species specific attractants (such as "pheromones", which are insect-produced volatile compounds attractive to both sexes in case of bark beetles) have been chemically identified and synthesized and it is sought to make use of such attractants particularly in traps adapted to the biology of the insect species.
The devices for catching bark beetles are usually divided into two types, such as "flight traps" and "landing traps". The principle of flight traps resides in that the insects, lured by the attractants collide "unintentionally" with a flight barrier invisible to them, then fall and are caught in some manner. The principle of landing traps resides in that the insects, lured by the attractant, "intentionally" land on the outer trap wall and run thereon until they have found an aperture through which they can pass. Then they have to crawl through the aperture into the trap, whereupon they fall directly into a collecting vessel positioned on the trap floor.
A flight trap for catching flying forest insects is disclosed, for example, in German Offenlegungsschrift (application published without examination) No. 2,924,629. The structure disclosed therein has two planar plates arranged at right angles which serve as collision surfaces or flight barriers. The plates are arranged on a funnel which has a smooth upper surface and which opens into a collecting vessel arranged therebelow. The collecting vessel accommodates a receptacle which contains the attractant. The beetles collide in flight with the plates which are invisible for them and fall--in case all components operate as intended--into the funnel and therefrom into the collecting vessel. In order to obtain satisfactory results with this type of insect trap, the surfaces of the plates as well as the funnel have to be sufficiently large. This results in the disadvantage that in addition to insects intended to be trapped, plant parts, other foreign bodies and sometimes even birds, drop into the funnel, so that its smooth surface is "roughened" by soiling. In early summer, particularly pollen is responsible for soiling the funnel surfaces. When the funnel surface loses its smoothness, the insects falling into the funnel do not slide into the collecting vessel, but are able to hold onto the funnel wall and frequently leave the trap and return to the woods. Because of the large funnel opening, rain, snow and wind also have a disadvantageous effect on the functioning of these types of traps. Thus, for the above-outlined reasons, this type of known trap is often in an inoperative condition.
A known landing trap is disclosed, for example, in German Offenlegungsschrift No. 2,821,378. The trap which has been designed particularly for bark beetles, has a hollow body which has a large number of passages situated on the top of the hollow body. The outer surface of the hollow body is roughened to permit the beetles to land and run thereon. The inner face of the hollow body is particularly smooth. The immediate vicinity of the passages on the inside of the hollow body is also roughened. Within the hollow body there is positioned a receptacle containing the attractant. It has been found that such a device is well adapted for catching bark beetles without endangering useful animals. By virtue of its particular shape, the trap is adapted precisely to the configuration of bark beetles while other forest insects cannot be trapped thereby or are only caught accidentally. Further, the known landing trap is significantly less efficient than flight traps because landing traps, as noted, set much higher "requirements" for the beetles.